- Radium (Ra) is a highly radioactive alkaline earth metal with atomic number 88, belonging to Group 2 of the periodic table beneath barium.
- Its electron configuration is [Rn] 7s², consistent with other Group 2 elements. The atom contains eighty-eight protons, and its most stable isotope, radium-226 (²²⁶Ra), has 138 neutrons and a half-life of about 1,600 years.
- Radium-226 is part of the uranium-238 (²³⁸U) decay series, decaying into radon-222 (²²²Rn), a radioactive noble gas. Several other isotopes exist, but all are short-lived compared to radium-226.
- Radium was discovered in 1898 by Marie Curie and Pierre Curie in Paris, France, through their pioneering research on uranium ore (pitchblende). After months of laborious chemical separation, they isolated radium chloride (RaCl₂) and later determined its remarkable radioactivity. Radium’s discovery was a cornerstone in the early study of radioactivity, for which the Curies were awarded the Nobel Prize in Physics in 1903, and Marie Curie later won the Nobel Prize in Chemistry in 1911 for her work in isolating pure radium.
- Chemically, radium behaves like a heavier analog of barium, forming a +2 oxidation state in its compounds. It readily reacts with water to produce radium hydroxide (Ra(OH)₂) and hydrogen gas, and with halogens to form radium halides such as radium chloride (RaCl₂) and radium bromide (RaBr₂). Pure radium metal is silvery-white when freshly prepared, but it quickly oxidizes in air, turning black. A distinctive property of radium compounds is their strong radioactivity, which causes them to glow faintly in the dark due to radioluminescence.
- Historically, radium was once used in luminous paints for watch dials, instrument panels, and clock faces, as well as in early medical treatments such as radiotherapy. However, these applications proved highly dangerous due to the element’s intense radioactivity, leading to severe health problems, most infamously seen in the “Radium Girls” who painted watch dials in the early 20th century. Today, radium is no longer used in consumer products and has been replaced by safer alternatives like tritium and phosphorescent materials.
- Biologically, radium has no beneficial role and is extremely hazardous. It behaves chemically like calcium and thus can accumulate in bones when ingested, where its radioactivity damages bone marrow and increases the risk of cancer.
- Environmentally, radium occurs naturally in trace amounts as part of uranium and thorium ores. It is a significant source of natural background radiation due to the production of radon gas during its decay. Strict safety measures are now required when handling or disposing of radium to protect human health and the environment.
